As a filament having discontinuous nodules randomly arranged perpendicularly to the filament axis, there has so far been known a polyester filament having randomly arranged, discontinuous circumferential ridges of submicroscopic size occurring with a frequency between 10 and 130 ridges per millimeter along the length of the filament (U.S. Pat. No. 3,184,369). Further, as a manufacturing process, there has been known a process comprising contacting an as-spun filament with a crack-promoting agent under tension to produce cracks, drawing the filament and then removing the crack-promoting agent (U.S. Pat. No. 3,185,613).
Other than the above, as a process for manufacturing filaments having nodules with a long axial pitch, there has been known a process for producing nodulous filament (having about 0.1-1.0 nodules per 10 mm) by utilizing melt fracture caused by spinning a polymer at a temperature in the vicinity of the melting temperature of the polymer (Japanese Patent Application Publication No. 38-11,851); a process wherein a cooling medium is sprayed immediately after spinning; a process comprising embossing filaments with a rough-surfaced roll during take-up of the filaments after spinning; etc.
in the above-described filament having randomly arranged, discontinuous nodules and its manufacturing process, the course of the process until the filament is obtained is very complicated and, further, the obtained filament is composed mainly of a polyester- or polyamide-based non-elastomer and so has no elastic property.
Alternatively, the process utilizing melt fracture not only produces filaments having nodules with a very long axial pitch but also tends to be lacking in a stabilized operability in spinning. Furthermore, the process of embossing with a rough-surfaced roll poses a problem such that only nodules with a long axial pitch are obtainable, or the like.
As described above, there has not, heretofore been known any filaments having a rough surface characterized by numerous nodules arranged with a short axial pitch, particularly, having a bellows-like structure with a rough surface as well as stretch recovery, which can be industrially easily manufactured.